Deglaciation sequences in the Permo-Carboniferous Itarare Group, Parana Basin, southern Brazil

The Late Carboniferous-Early Permian Itarare Group is a thick glacial unit of the Parana Basin. Five unconformity-bounded sequences have been defined in the eastern outcrop belt and recognized in well logs along 400 km across the central portion of the basin. Deglaciation sequences are present in the whole succession and represent the bulk of the stratigraphic record. The fining-upward vertical facies succession is characteristic of a retrogradational stacking pattern and corresponds to the stratigraphic record of major ice-retreat phases. Laterally discontinuous subglacial tillites and boulder beds occur at the base of the sequences. When these subglacial facies are absent, deglaciation sequences lie directly on the basal disconformities. Commonly present in the lowermost portions of the deglaciation sequences, polymictic conglomerates and cross-bedded sandstones are generated in subaqueous proximal outwash fans in front of retreating glaciers. The overlying assemblage of diamictites, parallel-bedded and rippled sandstones, and Bouma-like facies sequences are interpreted as deposits of distal outwash fan lobes. The tops of the deglaciation sequences are positioned in clay-rich marine horizons that show little (fine-laminated facies with dropstones) or no evidence of glacial influence on the deposition and likely represent periods of maximum ice retreat. (c) 2006 Elsevier Ltd. All rights reserved.

Camadas de tempestito grosso (coarse grained storm beds): exemplos do Permiano da bacia do Paraná

Tempestitos grossos constituem camadas delgadas de conglomerado gradando a arenito, com estratificação cruzada seguida de laminação ondulada truncante a simétrica e de drape/flaser de siltito/folhelho. Cinco exemplos extraídos do Permiano da bacia do Paraná ilustram esse tipo de depósito: três deles são de rochas siliciclásticas, contendo bioclastos de bivalves e vertebrados (Formação Rio Bonito-Membro Triunfo e Formação Palermo), enquanto os outros dois são de rochas carbonática e fosfática (respectivamente, formações Teresina e Corumbataí do Grupo Passa Dois). O componente tracional da base do tempestito grosso apresenta-se como arenite quartzoso/lítico ou grainstone oolítico com cimento calcífero preenchendo poros (casos das formações Palermo e Teresina). em sua maioria, os tempestitos grossos constituem pavimentos transgressivos intercalados em folhelhos ou tempestitos finos (arenitos muito finos a folhelhos com estratificação ondulada truncante-hummocky). em outro caso, extraído de subsuperfície, o pavimento transgressivo ocorre na base de uma sucessão progradante de barra de plataforma. O tempestito grosso da Formação Teresina constitui um evento transgressivo sobreposto a depósitos de barra de plataforma.

Plutonism in three orogenic pulses, Eastern Blue Ridge Province, southern Appalachians

The Eastern Blue Ridge Province of the southern Appalachians contains, in part, remnants of an Ordovician accretionary wedge complex formed during subduction of an oceanic tract before mid-Ordovician accretion with Laurentia. The Eastern Blue Ridge Province consists of metapelite and amphibolite intruded by low-K plutons, high-temperature (T > 750 degrees C) Ordovician eclogite, and other high-pressure metamafic and meta-ultramatic rocks. Felsic plutons in the Eastern Blue Ridge Province are important time markers for regional-scale tectonics, deformation, and metamorphism. Plutons were thought to be related to either Taconian (Ordovician) or Acadian (Devonian-Silurian) tectonothermal events.We dated five plutonic or metaplutonic rocks to constrain pluton crystallization ages better and thus the timing of tectonism. The Persimmon Creek gneiss yielded a protolith crystallization age of 455.7 +/- 2.1 Ma, Chalk Mountain 377.7 +/- 2.5 Ma, Mt. Airy 334 +/- 3 Ma, Stone Mountain 335.6 +/- 1.0 Ma, and Rabun 335.1 +/- 2.8 Ma. The latter four plutons were thought to be part of the Acadian Spruce Pine Suite, but instead our new ages indicate that Alleghanian (Carboniferous-Permian) plutonism is widespread and voluminous in the Eastern Blue Ridge Province. The Chattahoochee fault, which was considered an Acadian structure, cuts the Rabun pluton and thus must have been active during the Alleghanian orogeny. The new ages indicate that Persimmon Creek crystallized less than 3 m.y. after zircon crystallization in Eastern Blue Ridge eclogite and is nearly synchronous with nearby high-grade metamorphism and migmatization. The three phases of plutonism in the Eastern Blue Ridge Province correspond with established metamorphic ages for each of the three major orogenic pulses along the western flank of the southern Appalachians.

Comparative analysis of drilling frequencies in recent brachiopod-mollusk associations from the Southern Brazilian Shelf

Over 14,000 specimens-5,204 brachiopods, 9,137 bivalves, and 178 gastropods-acquired from 30 collecting stations (0 to 45 m depth) in the Ubatuba and Picinguaba bays, southern Brazil, were compared for drilling frequencies. Beveled (countersunk) circular-to-subcircular borings (Oichnus-like drill holes) were found in diverse bivalves but also in the rhynchonelliform brachiopod Bouchardia rosea-a small, semi-infaunal to epifaunal, free-lying species that dominates the brachiopod fauna of the southern Brazilian shelf. Drill holes in bivalve mollusks and brachiopods are comparable in their morphology, average diameter, and diameter range, indicating attacks by a single type of drilling organism. Drill holes in brachiopods were rare (0.4%) and found only at five sampling sites. Drillings in bivalves were over 10 times as frequent as in brachiopods, but the average drilling frequency was still low (5.6%) compared to typical boring frequencies of Cenozoic mollusks. Some common bivalve species, however, were drilled at frequencies up to 50 times higher than those observed for shells of B. rosea from the same samples. Due to scarcity of drilled brachiopods, it is not possible to evaluate if the driller displayed a nonrandom (stereotyped) site, size, or valve preference. Drilled brachiopods may record (1) naticid or muricid predation, (2) predation by other drillers, (3) parasitic drillings, and (4) mistaken or opportunistic attacks. Low drilling frequency in brachiopods is consistent with recent reports on ancient and modern examples. The scarcity of drilling in brachiopods, coupled with much higher drilling frequencies observed in sympatric bivalves, suggests that drilling in brachiopods may have been due to facultative or erroneous attacks. The drilling frequencies observed here for the brachiopod-bivalve assemblages are remarkably similar to those reported for Permian brachiopod-bivalves associations. This report adds to the growing evidence for an intriguing macroecological stasis: multiple meta-analytical surveys of present-day and fossil rhynchonelliform brachiopods conducted in recent years also point to persistent scarcity and low intensity of biotic interactions between brachiopods and drilling organisms throughout their evolutionary history.

Conchostráceos com linhas de crescimento recurvadas junto à margem dorsal (famílias Palaeolimnadiopseidae e Perilimnadiidae) da formação rio do rasto, Permiano superior, bacia do Paraná, Brasil

Some Upper Permian conchostracans from the Rio do Rasto Formation (Parana Basin, South Brazil) have very characteristic recurved growth lines at the dorsal margin. All previously described specimens were classified as Palaeolimnadiopsis subalata (Reed) Raymond. However, a re-analysis of these fossils and of additional recently- collected specimens demonstrated that not all can be included in a single species, nor only in the Family Palaeolimnadiopseidae. According to their shape and the size of the umbo, they are classified into three species. The sub-elliptic carapaces with small anterior umbo are maintained in Palaeolimnadiopsis subalata (Reed, 1929) Raymond, 1946. The sub-circular carapaces with small sub-central umbo correspond to the new species Palaeolimnadiopsis riorastensis. The small size of the umbo is a character of the Family Palaeolimnadiopseidae. The small elliptic valves with large anterior umbo are assigned to the new species Falsisca brasiliensis of the Family Perilimnadiidae, which is characterized by large umbos. Palaeolimnadiopsis has a wide chronostratigraphic distribution, but Falsisca is restricted to the Upper Permian-Lower Triassic of Europe and Asia. This interval is in agreement with the probable Late Permian age of the respective strata of the Rio do Rasto formation. Falsisca was not previously recorded in Gondwana.

A new Pennsylvanian Oriocrassatellinae from Brazil and the distribution of the genus Oriocrassatella in space and time

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Concepcoes estratigraficas em analise de Bacias: A) a estratigrafia tradicional

This article is the first part of an overall theme dealing with different stratigraphic approaches to basin analysis. The traditional stratigraphy, based on formal units, is discussed here with an attempt to analyse their principles, methods and purposes. Using the Permian carboniferous sequence of Parana Basin as a paradigm, some critical inferences concerning the limitations of such an approach in environmental reconstruction are attained. -English summary

Concepcoes estratigraficas em analise de bacias: C) a estratigrafia genetica

The present work fits the concepts of depositional systems and depositional sequence as paralithostratigraphic and parachronostratigraphic units, respectively, and discusses the advantages of using this approach in environmental reconstructions. The depositional system concept came to a focus as a link between sedimentology and stratigraphy since it represents both a facies association and a mapping unit. Additionally, the depositional sequence represents the sedimentary episode of relative sea level change, in interaction with basin paleophysiography. In such a way a time-space diagnosis is reached in environmental interpretation as illustrated by the Permian-Carboniferous sequence of the Parana Basin. -English summary

Marcos estratigraficos regionais na Formacao Palermo: caracterizacao dos picos radioativos

During a basinal scale study on Palermo Formation (Upper Permian, Parana Basin) high elevated Gamma Ray picks were identified mainly in the lower third of that stratigraphic unit. Those Gamma Ray signatures have been used as good regional stratigraphic markers. From them it was possible one chronostratigraphic analysis of Palermo Formation as pointed out by previous papers (Perinotto). Potassium40 is the responsible for the high Gamma Ray picks in the Palermo Formation. -from English summary

Gênese e Classificação da Coquina de Camaquã, Formação Corumbataí (Neopermiano), na Região de Rio Claro, SP

Analysis of the taphonomic signatures of a well preserved, silicifled coquina (Pinzonella neotropica assemblage) from the Camaquã outcrop, upper part of the Corumbataí Formation (Late Permian), in the Rio Claro region, state of Sáo Paulo, allowed interpretation of processes involved in its origin as related to high energy events (storms). The coquina occurs as a lenticular body, 2-11 cm thick and extending laterally for about 120 m. Basal contact of the coquina is sharp and erosive. Its upper contact is sharp. The concentration is dominated by pelecypods including the shallow burrowers (Pinzonella neotropica, Jacquesia brasiliensis), intermediate burrower (Pyramus anceps) and semi-infaunal forms (Naiadopsis lamellosus). All these species are suspension feeders. Besides sand-sized or even smaller shell fragments, there occur disarticulated, complete shells which are commonly abraded but do not show any signs of bioerosion or incrustation. In vertical side view, the shells are mainly convex-up, nested or stacked, while in plan-view they show random orientation. Multiple discontinuous grading is visible. These taphonomic signatures suggest that the origin of the skeletal accumulation is related to high energy events (possibly storm flows) in a proximal environment. The amalgamated nature of the Camaquã coquina records several episodes of erosion and deposition.

Tafonomia de Pelecípodes da Formação Teresina (Permiano), Tiaraju, RS, Brasil

Taphonomic analysis of pelecypod concentration in the part of the Teresina Formation (Passa Dois Group), Tiaraju region, State of Rio Grande do Sul, indicates its origins as due to high energy events (storms). The fauna include shallow-burrowing suspensivorous species, associated with this byssate semi-infauna species. Several taphonomic characteristics indicate that the fossiliferous assemblage was subject to little selective processes during transportation. These are: predominance of disarticulated valves (although articulated valves are frequent) and perpendicular, oblique, concordant and nested arrangement of bioclasts in the sedimentary matrix. Absence of fragmentation, bioerosion and incrustation of the bioclasts, suggest fast burial of shells due to high sedimentation rate events. Diagenetic features, indicate that the fossils were later submitted to refossilization and mixing with other non-coeval bioclasts, resulting in some degree of time-averaging.

Plutonismn in three orogenic pulses, Eastern Blue Ridge Province, southern Appalachians

The Eastern Blue Ridge Province of the southern Appalachians contains, in part, remnants of an Ordovician accretionary wedge complex formed during subduction of an oceanic tract before mid-Ordovician accretion with Laurentia. The Eastern Blue Ridge Province consists of metapelite and amphibolite intruded by low-K plutons, high-temperature (T >750 °C) Ordovician eclogite, and other high-pressure metamafic and meta-ultramafic rocks. Felsic plutons in the Eastern Blue Ridge Province are important time markers for regional-scale tectonics, deformation, and metamorphism. Plutons were thought to be related to either Taconian (Ordovician) or Acadian (Devonian-Silurian) tectonothermal events. We dated five plutonic or metaplutonic rocks to constrain pluton crystallization ages better and thus the timing of tectonism. The Persimmon Creek gneiss yielded a protolith crystallization age of 455.7 ± 2.1 Ma, Chalk Mountain 377.7 ± 2.5 Ma, Mt. Airy 334 ± 3Ma, Stone Mountain 335.6 ± 1.0 Ma, and Rabun 335.1 ± 2.8 Ma. The latter four plutons were thought to be part of the Acadian Spruce Pine Suite, but instead our new ages indicate that Alleghanian (Carboniferous-Permian) plutonism is widespread and voluminous in the Eastern Blue Ridge Province. The Chattahoochee fault, which was considered an Acadian structure, cuts the Rabun pluton and thus must have been active during the Alleghanian orogeny. The new ages indicate that Persimmon Creek crystallized less than 3 m.y. after zircon crystallization in Eastern Blue Ridge eclogite and is nearly synchronous with nearby high-grade metamorphism and migmatization. The three phases of plutonism in the Eastern Blue Ridge Province correspond with established metamorphic ages for each of the three major orogenic pulses along the western flank of the southern Appalachians. © 2006 Geological Society of America.

Conchostráceos com linhas de crescimento recurvadas junto à margem dorsal (Famílias Palaeolimnadiopseidae e Perilimnadiidae) da Formação Rio do Rasto, permiano superior, Bacia do Paraná, Brasil

Some Upper Permian conchostracans from the Rio do Rasto Formation (Paraná Basin, South Brazil) have very characteristic recurved growth lines at the dorsal margin. All previously described specimens were classified as Palaeolimnadiopsis subalata (Reed) Raymond. However, a re-analysis of these fossils and of additional recently- collected specimens demonstrated that not all can be included in a single species, nor only in the Family Palaeolimnadiopseidae. According to their shape and the size of the umbo, they are classified into three species. The sub-elliptic carapaces with small anterior umbo are maintained in Palaeolimnadiopsis subalata (Reed, 1929) Raymond, 1946. The sub-circular carapaces with small sub-central umbo correspond to the new species Palaeolimnadiopsis riorastensis. The small size of the umbo is a character of the Family Palaeolimnadiopseidae. The small elliptic valves with large anterior umbo are assigned to the new species Falsisca brasiliensis of the Family Perilimnadiidae, which is characterized by large umbos. Palaeolimnadiopsis has a wide chronostratigraphic distribution, but Falsisca is restricted to the Upper Permian-Lower Triassic of Europe and Asia. This interval is in agreement with the probable Late Permian age of the respective strata of the Rio do Rasto Formation. Falsisca was not previously recorded in Gondwana.

The first Triassic lungfish from South America (Santa Maria Formation, Paraná Basin) and its bearing on geological correlations within Pangaea

The Triassic fish faunas of the Southern Hemisphere are only known from a few sedimentary basins and the most productive sites are those from the Karoo Supergroup, in South Africa and the Sydney Basin of Australia. A single lungfish tooth plate ascribed to Ptychoceratodus cf. philippsi was recovered from Late Triassic (Carnian) red beds of southern Brazil and is described herein. This find extends to South America the palaeogeographic distribution of the genus, which occurs in the Early Triassic of Australia and South Africa and the Middle/Late Triassic of Europe and Late Triassic of Madagascar and India. The presence of this dipnoan solely in the uppermost part of the Santa Maria Formation suggests that the migration of Ptychoceratodus towards the Paraná Basin began not before the late Induan/early Olenekian (late Early Triassic). At that time, more humid (monsoonal) conditions prevailed in what is now southern Brazil, compared to semi-arid/desert conditions that dominated the Late Permian and possibly the earliest Early Triassic (the latter presumably not represented in the Paraná Basin). © The Geological Society of London 2008.

Diques clásticos na formação corumbataí (p) no nordeste da bacia do paraná, SP: Análise sistemática e significações estratigráficas, sedimentológicas e tectônicas

This paper aims to present the results of systematic survey on clastic dykes in the Corumbataí Formation (Permian), in the northeast region of the State of São Paulo. Besides this, the paper analyses genetic aspects of those features as well as their stratigraphic and sedimentologic implications in terms of geologic evolution of the northeastern Paraná Sedimentary Basin during Permian times. The field works had been developed in 3 main Corumbataí Formation outcrops (2 road cuts and a quarry) supposed to show the most important clastic dikes occurrences in the studied area. Basically, the sedimentary intrusions are formed by fine sand or silt size particles and had penetrated host rocks as near-vertical, centimeter thick, dykes (most common form) or as horizontal sheets, forming clastic sills (subsidiary form), both with variable geometric forms and dimensions. A lot of dyke walls show undulations suggesting pre-diagenetic clastic intrusions, probably near the ancient depositional surface. Almost all intrusions occur in the superior third portion of the Corumbataí Formation and some similar features seem to appear in the adjoining superposed Pirambóia Formation base. In this article the authors defend a seismic origin hypothesis for the clastic intrusions. It is important to mention that clastic intrusions tend to occur linked to expressive seismic events, with magnitude upper to 5. The analysis of isopach maps of the Permian and Mesozoic units of the Paraná Sedimentary Basin in the study area suggests a depositional system changing, from epicontinental sea conditions to shallow platform and, finally, to coastal deserts. Probably, this environmental change was driven by regional uplift accompanied by seismic events. It is possible that ancient seismicity triggered liquefaction processes and the resulting clastic intrusions. In this sense, those clastic features might be properly namedseismites.